The present invention relates generally to medical devices and particularly to an auger device for penetrating an occlusion.
Minimally invasive medical procedures have become common in the medical profession due to the lower risk and trauma associated with minimally invasive procedures and the lower cost compared to open surgical procedures. Minimally invasive procedures generally involve gaining access to a patient's internal vessel by puncturing the patient's skin, intermediate tissues between the skin and the vessel, and the wall of the vessel. An elongate medical instrument may then be inserted through the access site so that the distal end of the medical instrument is located within the patient's internal vessel, while the proximal end of the medical instrument remains outside the patient's body. The physician may then manipulate the proximal end of the medical instrument outside the patient's body to move and orient the distal end of the medical instrument to a location within the vessel where treatment is needed. Thus, a treatment site within a patient's vessel may be treated from outside the patient's body through a relatively small access site that is located some distance from the treatment site. By contrast, conventional open surgical procedures would require opening the tissues immediately adjacent the treatment site so that the surgeon can gain direct access to the treatment site.
One example of where minimally invasive procedures are commonly used is the treatment of stenoses and other occlusions within vessels using angioplasty techniques. Typically, angioplasty procedures are performed using a balloon-tipped catheter that may or may not have a balloon-expandable stent mounted on the balloon. In general, a physician performs an angioplasty procedure by introducing a balloon catheter into a peripheral artery (commonly one of the leg or arm arteries) and threading the catheter to the narrowed region of the artery. During this stage, the balloon is uninflated and collapsed onto the shaft of the catheter in order to present a low profile which may be passed through the arterial lumens. Once the balloon is positioned at the narrowed region of the artery, the balloon is expanded by pumping a mixture of saline and contrast solution through the catheter to the balloon. As a result, the balloon presses against the inner wall of the artery to dilate it. If a balloon-expandable stent is mounted on the balloon, the balloon inflation also serves to expand the stent and implant it in the artery. After the artery is dilated, the balloon is deflated so that it once again collapses onto the shaft of the catheter. The balloon-tipped catheter is then retracted from the arteries. If a stent is mounted on the balloon of the catheter, the stent is left permanently implanted in its expanded state at the desired location in the artery to provide a support structure that prevents the artery from collapsing back to its pre-dilated condition. Alternatively, the balloon catheter may be used to dilate a stenosis without implanting a stent. A balloon-expandable stent or self-expandable stent may then be implanted in the dilated region in a follow-up procedure. If desired, a physician may also dilate the artery and stent a second time after the stent is implanted with a balloon catheter.
However, some types of occlusions are difficult to treat with conventional angioplasty procedures. For example in the case of severe occlusions, the passageway extending through the occlusion may have become so narrow that a conventional balloon catheter and/or guidewire may not be able to pass through the occlusion. Moreover, some occlusions become completely blocked, also known as a chronic total occlusion (CTO), such that there is no longer any open passageway extending through the occlusion. In these cases, it may not even be possible to push a conventional guidewire through the center of the occlusion. In order to treat severe occlusions like these, some physicians have resorted to forcing the guidewire around the occlusion through layers of the vessel wall and then pushing the entire occlusion to the side with a balloon. However, this procedure causes undesirable trauma because the inner layers of the vessel wall where the guidewire penetrated are torn away as the occlusion is pushed aside.
Another type of occlusion that may be difficult to treat with conventional procedures is hardened occlusions. Hardened occlusions may have a buildup of atherosclerotic plaque or other substances that is difficult to penetrate and/or dilate. A hardened occlusion is also a common condition of severe occlusions described above. For example, once an occlusion becomes completely occluded as in the case of a CTO, the upstream side of the occlusion often forms a fibrous, hardened cap that is difficult or impossible to penetrate with conventional devices. However, even partial occlusions where a conventional balloon catheter is passable may become so hardened that a conventional balloon cannot dilate the occlusion with conventional balloon pressures.
Accordingly, the inventors believe it would be desirable to provide a guidewire with an auger-like tip that could drill through an occlusion.